1. Field of the Invention
Aspects of the present invention relate to an organic light emitting diode (OLED) display device, and a method of manufacturing the same, and more particularly, to an OLED display device, which includes a conductive material layer and a metal layer disposed between a cathode and an encapsulation substrate, can prevent a voltage applied to a cathode from dropping, can reflect ambient light, and has improved mechanical reliability.
2. Description of the Related Art
Generally, an organic light emitting diode (OLED) display device is a self-emissive display that electrically excites organic compounds to emit light. An OLED display device may be categorized as a passive matrix OLED display device, or an active matrix OLED display device, depending on how unit pixels of an N×M matrix are driven. Compared with the passive matrix OLED display device, the active matrix OLED display device is more suitable for large-area display devices, due to its lower power consumption and higher resolution.
FIG. 1 is a cross-sectional view of a conventional OLED display device. Referring to FIG. 1, a buffer layer 110 is formed on a substrate 100, which can be an insulating glass substrate, a conductive substrate, or a plastic substrate. An amorphous silicon (a-Si) layer is formed on the buffer layer 110, and crystallized into a polysilicon (poly-Si) layer, to form a semiconductor layer 120 on the buffer layer 110.
A gate insulating layer 130 is formed on the entire surface of the substrate 100 and the semiconductor layer 120. A gate electrode 140 is formed on the gate insulating layer 130 at a predetermined region of the semiconductor layer 120. An interlayer insulating layer 150 is formed on the entire surface of the substrate 100 and the gate electrode 140, and is etched to expose predetermined regions of the semiconductor layer 120, thereby forming contact holes.
A source/drain electrode material is deposited on the entire surface of the substrate 100, and patterned to form source and drain electrodes 161 and 162. The source and drain electrodes 161 and 162 are connected to the predetermined regions of the semiconductor layer 120. A planarization layer 170 is formed on the entire surface of the substrate 100, and etched to form a hole to expose one of the source and drain electrodes 161 and 162. A first electrode 180 is formed on the planarization layer 170, and is connected to one of the source and drain electrodes 161 and 162.
Subsequently, a pixel defining layer 190 is formed to expose the first electrode 180. An organic layer 200 is formed on the first electrode 180 and the pixel defining layer 190. A second electrode 210 is formed on the entire surface of the substrate 100. The substrate 100 is combined with an encapsulation substrate 220, using an encapsulant 230.
In a conventional bottom-emitting structure, as described above, the encapsulation substrate 220 not emitting light is not used for any purpose, other than to support an absorbent. Also, since the second electrode 210 is formed on the entire surface of the substrate 100, a voltage applied to the second electrode 210 may drop. Non-uniform voltages are applied to respective pixels, therefore, the pixels do not have uniform emission characteristics. Furthermore, when an external shock is applied to the encapsulation substrate 220, the encapsulation substrate 220 may collapse, and contact the top surface of the OLED display device, due to a gap between the substrate 100 and the encapsulation substrate 220, thereby damaging the OLED display device.